Q. I've read every issue of STREET RODDER, and every article you've written. I consistently see abrasive cut-off wheels used in the patch panel articles.
I TIG weld, and I've learned that the material has to be super clean. All of my structural cutting is done with a Makita "dry-cut" saw, which has a carbide-tipped blade. I use an angle grinder to ease the edges of thick material to get sufficient penetration. I have occasionally had problems with contamination; I've seen the dreaded shiny black bubble dancing on the top off my weld. This means it's start over time, and I clean the joint with a drill bit, followed by carbide burrs.
So, when using an abrasive cut-off disc, shouldn't the edge be cleaned with a few passes of a file? Would a wire brush attachment clean the edge?
Via the Internet
A. Sounds like you're a real enthusiast, and I can see you have a lot of experience under your belt. Like you say, TIG welding is extremely sensitive to any sort of contamination, and even barely perceptible traces of contaminants can foul the weld. I do quite a bit of welding on edges that I trim with an abrasive cut-off wheel. Before welding, I usually clean the parts by sanding, and with a degreaser if necessary, and it's pretty rare that I have a problem with contamination.
There are a couple of possible causes for contamination from an abrasive disc. As the disc wears, it makes a lot of dust, and this could be a contaminant, but the dust is pretty easy to brush or blow off. With steel, I've found that discoloration caused by the heat of cutting can cause welding problems. I'm always careful to sand any burrs or discoloration off. Yes, a file or wire brush could work too. A dry-cut carbide-toothed blade is a good way to cut structural steel, but they are not designed for cutting sheetmetal. As long as everything you're welding is free of contamination, I don't think it matters how the metal was cut.
Q. What are your thoughts on a shrinking in the English wheel? I know that the English wheel generally works by stretching metal. Do you think a serrated wheel would shrink metal as it rolls through? Is it even possible to use the wheel to shrink?
I have an English wheel and a standard Eastwood shrinker/stretcher. I don't like going back to the wheel to correct flat spots put in by the shrinking jaws, then over stretch it, and have to shrink again.
Via the Internet
A. The English wheel and the shrinking machine use opposite principles to form metal. The English wheel works metal by stretching it. If the gap between the wheels is slightly smaller than the thickness of the metal being worked, the metal is squeezed slightly between the wheels and it bulges out in all directions, causing the metal to dome.
A mechanical shrinker has jaws that grip the metal, and draw together, "gathering" the metal, and making it slightly thicker. The shrinker jaw faces have texture to allow them to grip the metal, but the serrations alone don't do the shrinking; it's primarily the motion of the jaws moving toward each other. Now, you can probably see why simply using a serrated wheel in an English wheel wouldn't cause metal to shrink.
There is a very specialized situation in which an English wheel can be used to shrink metal to some degree. If you have a domed panel, with a small, localized high spot, sometimes you can cause the high spot to be pushed down by carefully wheeling across it, with very low pressure between the wheels. You can even form "ruffles" in the edge of a panel, and if they are carefully wheeled flat, this will shrink the metal, too. This is not a common way to use the wheel, but I've done it, and it works well in certain instances.
You can email your questions to Professor hammer at email@example.com, or mail to: Covell Creative Metalworking, 106 Airport Blvd,. Suite 105, Freedom, CA 95019; you'll receive a personal reply. Ron Covell has made many DVDs on metalworking, and he offers an ongoing series or workshops across the nation. Check them out online at covell.biz, or call for a current schedule of workshops and a free catalog of DVDs. Phone (800) 747-4631, or (831) 768-0705. You'll also enjoy Ron's YouTube channel: youtube.com/user/covellron